The present invention relates to a spreader system mounted on a truck. More particularly the invention pertains to a twin discharge conveyor used to convey material from a truck mounted storage container to a desired application point.
Known spreader trucks convey materials, such as salt, sand and or salt/sand mixtures, from a storage container to a desired application point. The storage container mounted on the truck can be in the form of a combination dump box or combination sander body or V-Box hopper spreader. The spreader trucks are used to spread anti-icing and traction material on highways and roadways. It is known to provide a longitudinal conveyor positioned below the storage container and oriented along the axis of the storage container to convey the materials to either the front of the storage container or the rear of the storage container for discharge. If the material is moved along the longitudinal conveyor to be discharged at the front of the truck, the material can be dumped from the longitudinal conveyor onto a cross conveyor which then moves the material either to the left or to the right and thereafter discharges the material onto a spinner. The cross conveyors may be constructed using belting or chains or a screw auger, but in every case the movement of the conveyor is in a singular direction either to the left or to the right of the truck. In the case where a split conveyor is provided, with one conveyor being capable of moving material to the left of the truck and a second conveyor being capable of moving material to the right of the truck, the material is directed evenly to both conveyors, such as by pouring the material over a V-shaped dividing partition that directs half of the material to one conveyor and the other half to the second conveyor, or by shifting the longitudinal conveyor to dump all the material on one or the other of the cross conveyors. When it is desired to only spread material to one side of the truck, only the cross conveyor that moves material to that side of the truck is operated. A problem with the split conveyor system, however, is that an unacceptable amount of material continues to be discharged from the side of the truck where it is not wanted. The undesired leakage of material on the side of the truck where a cross conveyor is not being operated occurs as material continues to be divided evenly to both sides of the truck and the build up of material on the side of the truck where the conveyor is not operating results in continued leakage of material to that side of the truck.
In view of the above disadvantages of prior art spreader trucks, the present invention is directed to a twin discharge conveyor mounted to the chassis of the truck in front of a frame mounted material storage container, with the twin discharge conveyor being controllable by an operator to discharge material to either the left, the right, or both left and right sides of the equipped vehicle chassis. The twin conveyor can also be mounted at the rear of the frame mounted material storage container when a main longitudinal conveyor for moving material from the storage container to the twin conveyor operates in rear discharge mode. In a preferred embodiment of the invention, the twin discharge conveyor includes two augers mounted parallel to each other in a conveyor trough that is mounted to the chassis of the truck in front of the frame mounted material storage container. The twin cross conveyor can also include two belts or two chains mounted parallel to each other in a rectangular open conveyor box. The function and operation are similar to that of a twin auger conveyor.
The material can be moved along a longitudinal conveyor that is positioned underneath the storage container or can even form an integral bottom of this storage container, and dumped through a gate into the conveyor trough mounted crosswise at the front of the storage container. The two parallel mounted augers can be independently operated, such as by hydraulic motors. The hydraulic motors can be mounted at one end or the other of the augers and can be of various types including vane motors, gear motors or piston motors. In a preferred embodiment the hydraulic motors are gerotor motors, which are internal gear motors that can be driven at different rates of speed depending on the flow rate of hydraulic fluid provided to the motor. By controlling the flow of hydraulic fluid to the motors, the twin discharge conveyor can be operated with only one auger being rotated in a direction to move material to a first side of the vehicle, both augers being rotated in a direction to move material to the first side of the vehicle, only one auger being rotated to move material to a second side of the vehicle, both augers being rotated to move material to the second side of the vehicle, or one auger being rotated to move material to the first side of the vehicle while the second auger is rotated in the opposite direction to move material to the second side of the vehicle. The independent control of the motors operating the augers also allows the rates of speed of the two augers to be controlled independently, such that various ratios of the amounts of material being discharged to the first side and/or the second side of the vehicle can be achieved.
The rate at which material can enter the conveyor trough can be controlled by controlling the opening of a gate, and the rate of speed of the augers can be controlled independently to achieve the desired distribution of material per distance traveled by the spreader truck. Each end of the conveyor trough can also be provided with adjustable chutes and spinners that are adjustable vertically as well as horizontally. The chutes direct the material moved to the sides of the truck by the augers onto the spinners that then distribute the material in a desired pattern. The position of the chutes is adjustable so that material is dumped onto the spinners at different positions to achieve the desired distribution pattern. The spinners can also be rotated out of the way so that material is simply dumped from the discharge chutes onto the roadway to leave furrows of the material along one or both sides of the truck.
A spreader truck having the twin discharge conveyor according to an embodiment of the invention has the capability of accommodating road conditions that require the application of more material to one side of the chassis of the truck than the other. The rate at which the material is discharged from the twin discharge conveyor according to the invention to each side of the vehicle can also be varied. The vehicle operator can therefore regulate the placement of material so that it is applied where it is needed most. The conveyor trough is also designed to conform closely to the configuration of the two parallel augers, so that material placed into the conveyor trough is distributed only where it is desired, and little or no waste of the material occurs.